Using direct-lvm
requires a free block device. DigitalOcean Droplets are setup with a single partition by default which makes this slightly difficult. Though with the addition of block storage (currently in beta), it becomes much easier.
For example, booting up a new 16.04 Droplet with Docker installed and a block storage volume attached, we can see the free device at sda
as well as the loopback device created by Docker’s defaults:
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 100G 0 disk
vda 253:0 0 30G 0 disk
└─vda1 253:1 0 30G 0 part /
loop0 7:0 0 100G 0 loop
└─docker-253:1-784525-pool 252:0 0 100G 0 dm
loop1 7:1 0 2G 0 loop
└─docker-253:1-784525-pool 252:0 0 100G 0 dm
For all the information setting up direct-lvm mode for production see the Docker documentation. Though, here’s a quick run through. First we will stop Docker and then create a new volume and thin pool.
- sudo systemctl stop docker
- rm -rf /var/lib/docker/*
- pvcreate /dev/sda
- vgcreate docker /dev/sda
- lvcreate --wipesignatures y -n thinpool docker -l 95%VG
- lvcreate --wipesignatures y -n thinpoolmeta docker -l 1%VG
- lvconvert -y --zero n -c 512K --thinpool docker/thinpool --poolmetadata docker/thinpoolmeta
Now edit the file /etc/lvm/profile/docker-thinpool.profile
to configure auto-extending of the thin pool:
/etc/lvm/profile/docker-thinpool.profile
activation {
thin_pool_autoextend_threshold=80
thin_pool_autoextend_percent=20
}
Next, apply the change:
- lvchange --metadataprofile docker-thinpool docker/thinpool
Then, we will configure Docker itself to use the new device. This can be done with command line arguments when starting Docker, but with systemd it is simpler to edit /etc/docker/daemon.json
to include:
/etc/docker/daemon.json
{
"storage-driver": "devicemapper",
"storage-opts": [
"dm.thinpooldev=/dev/mapper/docker-thinpool",
"dm.use_deferred_removal=true"
]
}
Finally, let’s restart Docker:
- systemctl daemon-reload
- systemctl start docker
Now that we’re done, you can see that the loopback device is gone and sda
has been configured for LVM:
# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 100G 0 disk
├─docker-thinpool_tmeta 252:0 0 1020M 0 lvm
│ └─docker-thinpool 252:2 0 95G 0 lvm
└─docker-thinpool_tdata 252:1 0 95G 0 lvm
└─docker-thinpool 252:2 0 95G 0 lvm
vda 253:0 0 30G 0 disk
└─vda1 253:1 0 30G 0 part /